All my worlds have been corrupted by the new memory saving update.

I load Minecraft and find all my worlds grey and when i click on them it says syncing world then a pop up says that the world couldn't be synced or is corrupted. I try to load them multiple times but it keeps repeating that message.    Don't change how worlds are saved to "save space" when they are only a couple 100 MB because know i've lost a world that i have been working on for 4 YEARS😣